1. Field of the Invention
This invention relates to automatic package forming, filling and sealing machines involving fasteners, for example with complementary male and female profiles. This type of machine is often referred to as an FFS (“Form, Fill and Seal”) machine.
2. Description of the Prior Art
U.S. Pat. No. 4,909,017 to McMahon et al. describes a process in which bags are provided with a fastener when they are formed on an FFS machine. The bags are formed from a film of thermoplastic material. The film is in the form of a strip of material extending between two free edges that are longitudinal with reference to the movement of the film. This film is unrolled upstream of a filling tube. The fastener is positioned on the film, also upstream of the spout and transversely with respect to the direction of movement of the film. The fastener consists of two strips provided with complementary profiles. A first strip of the fastener is welded to the film upstream of the tube, on a portion of the film which is intended to form a first bag wall. The bag is then formed by enveloping the tube and welding the two longitudinal edges of the film. The second fastener is then welded below the tube to a second bag wall.
U.S. Pat. No. 4,655,862 to Christoff et al. also describes a process for forming reclosable bags on FFS machines, in which bags are provided with a fastener that is positioned at right angles to the direction of formation of these bags. This fastener is placed below the filling tube on a film in the form of a single strip. This strip includes at least one fold zone crosswise to the strip so that the strip can be folded back on itself, and areas of the strip that can work together to seal the bag can be brought opposite one another.
It is therefore an object of the present invention is to make the steps involving the support, welding and installation of the fastener on the film easier to perform than in the processes described in the above-cited references.